It is known that pipe in technical plants is exposed to corrosive attack. This applies to pipe, which is in operation as well as to pipe out of operation. The condition of pipe material therefore has to be carefully controlled. Corrosive attack takes place in particular at positions on the external wall, where pipe rests on supports or where pipe is fixed by pipe-clamps. corrosive attack is also observed for example beneath coats of paints or at the internal wall of pipe in these areas. Corrosion can be detected by physical methods. By these methods it can be determined, whether only slight, medium or heavy corrosive destruction of pipe material has taken place. They also permit the determination of remaining wall thickness.
One of the methods, which are technically applied, is ultrasonic testing. By using this method, pipe which is to be investigated and which rests on supports, has to be lifted by at least 100 mm. It is also necessary to clean and polish respectively grind the parts to be tested.
Pipe corrosion can also be determined by application of gamma ray or x-rays radiation. If this method is applied in the support area, again pipe has be lifted by at least 50 mm.
In order to determine corrosion below pipe-clamps, pipe has to be supported provisionally and the pipe-clamp has to be opened.
Lifting of pipes usually is associated with considerable requirements. Pipes have to be taken out of operation and have to be purged, flanges have to be disconnected and dependent on the size of pipe, heavy lifting utilities have to be employed. In addition, units, which are connected to pipes to be tested, often have to be shut down. As a consequence, losses of production have to be accepted. An additional disadvantage in conventional testing procedures is the risk of breaking pipe at corroded positions during lifting. This may also quite easily happen, if pipe is lifted by forcing wedges between pipe and support.
Although corrosion testing of pipe is carried out in countless units, no testing procedure is available, which permits testing of pipe resting on supports or clamped by pipe-clamps, without being forced to lift the pipe above the support or to open the pipe-clamp or even to shut down the units connected to the pipe to be tested.
The instant invention provides an improved method to the artisan for controlling corrosion by using gamma-ray radiation or x-ray radiation at the support and clamp area without the disadvantages of the state of the art described above.